Such case catches are well known. Hitherto, commercially successful designs have been manufactured from mild steel as a series of components, some of which are pressings and the post has been a turned part. For aesthetic and practical purposes the parts have been plated for example chromium plated. It is desirable to make the catches of stainless steel, but this has been found to be unexpectedly difficult in ordinary commercial quantities at economically acceptable prices due to difficulties in making turned parts from stainless steel, and to constraints in the availability of appropriately dimensioned material for the pressings. The object of the invention is to solve these problems.
According to the invention, a case catch comprises a drive mechanism including an axially short post made as a stack of sheet metal pressings including an intermediate pressing which lies in a journal aperture in the said one part and is sandwiched between a face plate and a locating plate which lie on opposite sides of the aperture, all of the parts of the stack being coupled together.
Preferably the coupling is a pair of rivets with axes located on a diameter of the parts and symmetrically of the axis of rotation. Conveniently one of the rivets mounts the crank where this is used.
One of the problems faced by the inventor is that stainless steel sheet for the pressings is made in a limited range of thicknesses, for example one millimeter, two millimeter and so on. To have sheet rolled to a different "special" thickness is uneconomic especially if it is wanted for a small component required in relatively small quantities. The said intermediate pressing used in the present invention is to lie in and be journalled for easy turning in an aperture in a hole in a different part, herein called the housing. To retain it in position it is sandwiched between the face plate and the locating plate which are also, in the invention, pressings which thus lie on opposite faces of the housing and these three (inter alia) are rivetted together. If the intermediate plate is made of the same thickness metal as the housing, the riveting will cause it to be too stiff for easy turning. If the intermediate plate is made of the next thicker grade of sheet metal available, it is likely to be too free in turning and be unsatisfactory for additional reasons. (In the case of a turned part it would obviously be possible to control the width of the groove which is equivalent to the thickness of the intermediate plate thus avoiding the problem). The inventor solves this difficulty by pressing a generally annular rib from the face of the intermediate plate so as to make it effectively axially thicker. The height of the rib can be easily controlled to give the required running clearance. Instead of using an annular rib, spaced dimples could produce a like effect.
The finger plate desirably folds flat when not in use, and is spring urged to either the flat or erect position. According to the invention this is achieved by making the finger plate as a pressing with axially aligned trunnion parts which have flat faces, and journalling the trunnions in the locating plate which may also be of a thinner material than the finger plate. Spring loading may be provided by a spring ring or Circlip (RTM) trapped in the cavity to overlie both trunnions, and held in place by a bridge plate extending transversely of an axis containing both trunnions. The bridge plate and locating plate may be held by the previously discussed rivets as part of the same assembly. When the finger plate is turned about the trunnions axis the flats, or their edges, deflect the spring at diametric positions, but the retention of the spring against deflection by the bridge plate creates a restoring force to return the finger plate or snap it to the next alternative position.